LOS ANGELES – Documentarians can be a dogged bunch, but put a prize in their path, and you'll really find out how relentless they are.

With the recent announcement of the 15 documentary features on its shortlist of Oscar contenders, the Academy of Motion Picture Arts and Sciences unleashed one of its most fearsome rites: a sharp-elbowed stampede by nonfiction filmmakers for one of five nomination slots that can save their pictures from obscurity.

The documentary competition has been growing more rambunctious as nonfiction film has evaporated from theaters. This year, only one — Disney's "Bears," with $17.8 million in domestic ticket sales — clawed into the box office Top 100 (No. 96). That economic reality has put extreme pressure on directors, producers and distributors to score a nomination. Oscar recognition, even just a nomination, should bring enough attention to grab viewers through video-on-demand and subscription services.

"The challenge with documentary is always getting people interested, and a nomination can work wonders," said Genna Terranova, director of the Tribeca Film Festival.

This year, more than any in memory, Terranova said, the shortlist field is exceptionally strong, heightening the competition.

Even with her famous family name and stature as a member of the Academy's documentary branch executive committee, Rory Kennedy, for instance, was quick out of the gate after her "Last Days in Vietnam" made the shortlist. The day after the list was released, she sent invitations to a "Last Days in Vietnam" holiday party at the Chateau Marmont.

The flip side of the shortlist's importance was evident in the Academy's snub of "Red Army," about Soviet-era hockey players. Sony Pictures Classics immediately pushed back its planned rollout of the movie.

Among the shortlisted films — winnowed from 134 eligible — there are various tensions: award stalwart (the Weinstein Co.) vs. deep-pocketed newcomer (Netflix), and the legacy of Roger Ebert vs. a nephew of his reviewing partner, Gene Siskel.

But the most prominent pressure point might be topical. The shortlisted films, which will be culled to five on Jan. 15 by the 224 filmmakers in the Academy's documentary branch, mostly fall into two groups of polar opposites: issues and arts.

The movies in the issues cluster — such as Laura Poitras' "Citizenfour," about the whistleblower Edward Snowden, and "The Case Against 8," a look at the campaign to legalize same-sex marriage — in many cases exhibit political content so strong that a vote for the film is essentially a vote for a position.

But the warmer-and-fuzzier arts camp, to the consternation of some of the more serious-minded filmmakers, has been winning this category lately. "Searching for Sugar Man," about the rediscovery of a rock star, won the best documentary Oscar in 2013. The backup-singer movie "20 Feet From Stardom" won the last go-round.

So the momentum is clearly with the entertainment cluster, which this time includes films like "Life Itself," a portrait of Ebert.

Conventional wisdom among close watchers of the Academy's documentary branch, which swaps thoughts on a members-only digital bulletin board, holds that two of the five nominations are locked up by "Citizenfour" and "Life Itself." Both are supported by powerful awards machines.

Among the backers of "Citizenfour" are the Weinstein Co., HBO and Participant Media. "Life Itself," directed by Steve James, is supported by Magnolia Pictures and CNN Films. Along with the Academy's presumed warmth for Ebert, who died last year, James likely will benefit from residual embarrassment over the Academy's famous snub of his "Hoop Dreams," an acclaimed basketball film whose failure to get a best documentary nomination in 1995 led to voting reform.

A third front-runner, "Keep on Keepin' On," also comes from Weinstein, which powered "20 Feet From Stardom" to the big prize. "Keep on Keep­in' On," about 93-year-old jazz trumpeter Clark Terry, muscled to the shortlist with some help from a mid-November screening at the Los Angeles home of Quincy Jones, who is among its producers.

If that wisdom can be trusted, that leaves 12 films competing for two slots. They include "Finding Vivian Maier," which was codirected by Charlie Siskel, a nephew of Gene Siskel, who was for years Ebert's film reviewing partner. "Finding Vivian Maier" recounts the career of a nanny who, only after her death, became recognized as a skilled street photographer.

Also getting attention are "Jodorowsky's Dune," a portrait of an eccentric filmmaker and his failed attempt to make a movie from Frank Herbert's epic "Dune," and Orlando von Einsiedel's "Virunga," from Netflix, about protecting mountain gorillas.